The supermodel is asking Pinault, heir to a $11.5 billion family estate, for a record-breaking $46,000 a month in child support. The pair will meet in Manhattan Family Court Thursday.
Evangelista dated Pinault for four months at the end of 2005 and was pregnant with "Augie" when Pinault began dating Hayek in April 2006. Pinault and Hayek have been married since 2009 and have a 4-year-old daughter, Valentina.
Evangelista, 46, says she needs the money for round-the-clock care, a driver and armed bodyguards for her son, according to the New York Daily News. "I need to protect him," she told Love magazine in February.
When a judge questioned the supermodel's need for full-time nannies, she responded, according to the Daily News, "When I work, it can be a 16-hour day. On days when I do not work, I am working on my image. I have to hit the gym. I have beauty appointments. I have to work toward my next job and maintaining my image, just like an athlete."
Famed divorce lawyer Raoul Felder told ABCNews.com that he believes Evangelista's claims are unrealistic. "It's the triumph of illusion over reality," he said. "That's all this is, a fairy tale."
"If she were married to him, that's a whole other story," he added.
Felder pointed out that even billionaire businessman Ron Perelman's ex-wife Patricia Duff, herself a millionaire, only received $12,000 a month in child support for their daughter, Caleigh.
For his part, Pinault has defended himself against the perception that he has been a deadbeat dad.
"At every possible opportunity he has participated in my family life whether in France or the United States," he said of Augie, who, under French law, stands to inherit one-quarter of his father's estate. "He is totally integrated within my family," Pinault said.
Pinault, 49, is chief executive of PPR, the conglomerate that owns Yves Saint Laurent, Gucci and Bottega Veneta. Dubbed the "King of Luxury," Pinault owns homes in Paris and Los Angeles. His family estate includes Christie's auction house, Château-Latour vineyard in Bordeaux and French premiere league football team Stade Rennais, the Daily News reported.
The 1980s supermodel is no slouch herself. She is worth $8 million and owns a downtown Manhattan penthouse as well as an Upper East Side apartment near her son's school, according to the Daily News.
She broke up last year with billionaire Peter Morton, the co-founder of the Hard Rock Cafe, and soon after, filed her case against Pinault. Since then, Pinault has been paying an undisclosed amount in child support for Augie and financing his health care and education, the Daily News reported.
But Evangelista, who kept the identity of Augie's father secret until she filed court papers in July, wants more. She is also demanding that Pinault provide her son a home equal to the $13 million California mansion he put in a trust for his daughter, Valentina.